<Collapse Bordered="false"
          DefaultActiveKey="@(new[]{"1"})"
          Class="site-collapse-custom-collapse">
    <ExpandIconTemplate>
        <Icon Type="caret-right" Rotate="@(context ? 90 : 0)"></Icon>
    </ExpandIconTemplate>
    <ChildContent>
        <Panel Header="This is panel header 1" Key="1"
               Class="site-collapse-custom-panel">
            <p>@text</p>
        </Panel>
        <Panel Header="This is panel header 2" Key="2"
               Class="site-collapse-custom-panel">
            <p>@text</p>
        </Panel>
        <Panel Header="This is panel header 3" Key="3"
               Class="site-collapse-custom-panel">
            <p>@text</p>
        </Panel>
    </ChildContent>
</Collapse>

@code{

    string text = @"
A dog is a type of domesticated animal.
Known for its loyalty and faithfulness,
it can be found as a welcome guest in many households across the world.
";

}

<style>
    [data-theme='compact'] .site-collapse-custom-collapse .site-collapse-custom-panel,
    .site-collapse-custom-collapse .site-collapse-custom-panel {
        background: #f7f7f7;
        border-radius: 2px;
        margin-bottom: 24px;
        border: 0px;
        overflow: hidden;
    }
</style>